Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (26 page)

   Mildly abnormal liver function tests, particularly increased aspartate aminotransferase (AST) and alkaline phosphatase (ALP) levels in nearly one third of patients.

   Increased interleukin-6 (IL-6); levels are related to disease activity.

   Biopsy of the involved arterial segment (commonly the temporal artery) and imaging studies can support the diagnosis.

Suggested Reading

Borchers AT, Gershwin ME. Giant cell arteritis: a review of classification, pathophysiology, geoepidemiology and treatment.
Autoimmun Rev.
2012;11(6–7):A544–A554.

GRANULOMATOSIS WITH POLYANGIITIS (WEGENER GRANULOMATOSIS)

   Definition

   Granulomatosis with polyangiitis (GPA), also referred to as Wegener granulomatosis (WG), is a multisystem autoimmune disease characterized by granulomatous inflammation and vasculitis of small and medium-sized vessels. The disease is often associated with the presence of ANCAs and most commonly affects the upper and lower respiratory tracts and kidneys.

   Microscopic polyangiitis is another ANCA-associated vasculitis that is similar to GPA and can be distinguished by the absence of granuloma formation.

   See Table
2-1
.

   Who Should Be Suspected?

   Likely candidates are patients presenting with constitutional symptoms (e.g., fever, malaise, arthralgia, weight loss) and severe upper respiratory findings including sinusitis, persistent rhinorrhea, purulent or bloody nasal discharge, nasal ulcers, cough, dyspnea, and hemoptysis. Renal disease is also common in GPA patients and characterized by asymptomatic hematuria. Other involved organs include the skin (50% of patients), eyes (e.g., conjunctivitis, corneal ulceration, retinal vasculitis), nervous system, or other internal organs. There is a high incidence of deep venous thrombosis in GPA patients.

   Both genders are equally affected, and the disease is far more common in white individuals.

   Laboratory Findings

   Approximately 90% of patients with active disease have ANCAs, with mostly a cytoplasmic staining pattern (c-ANCA). In most cases, antibodies associated with this pattern are directed against proteinase-3 (PR3) located in the azurophilic granules of neutrophils. Few GPA patients may have anti-MPO antibodies, which are typically associated with a perinuclear staining pattern (p-ANCA). This MPO-ANCA pattern is primarily associated with microscopic polyangiitis and eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome).